The goals of this project are the synthesis of short polynucleotides of known base sequence for the study of DNA structure and the interaction between DNA and intercalating drugs, and the improvement of the triester synthesis method of DNA synthesis. X-ray structure analyses are under way for d(CpCpGpG) and the low-and high-salt forms of d(CpGpCpG). Small crystals of intercalation compounds are being examined for suitability for analysis. Lac operator and its symmetrized analog are being synthesized in 50-mg quantities. Research in improvements in the triester synthesis will focus on finding better protecting groups for internucleotidic phosphate bonds and rapid synthesis of the starting blocks: mono-, di- and tri-nucleotides.